Container with discharging device

ABSTRACT

Containers for collecting and discharging particulate lignocellulosic material are disclosed, including a cylindrical upper portion, a lower portion tapering towards a bottom elongated space, an exit pipe below the bottom, a pair of parallel screws mounted on parallel shafts in the elongated space in a common horizontal plane for feeding the particulate lignocellulosic material towards the exit pipe, a pair of distributors disposed on the parallel screws above the exit pipe comprising radial discs, and a pump below the exit pipe for transporting the particulate lignocellulosic material to a subsequent step.

FIELD OF THE INVENTION

[0001] The present invention relates to a container for the collectingand discharging of particulate lignocellulosic material.

BACKGROUND OF THE INVENTION

[0002] In connection with the manufacture of papermaking pulp, varioussteps of the process include material being transported in the form ofchips or pulp. In certain parts of the process the material must be feduniformly from containers for storage and/or treatment of the materialto a subsequent treatment step, for example, the feeding of chips from astorage container to a digester. The problem in this case is to bringabout a uniform flow through the container. The material can adhere tothe walls of the container and thereby cause arching and/or the materialcan move at different speeds in different parts of the cross-section ofthe container. The feed of the material through the container can thusbe stopped, or the stay-time of the material in the container can vary.This is particularly unfavourable when the material is subjected to somekind of treatment in the container, for example preheating with steam ortreatment with chemicals.

[0003] Many different solutions of the above problem have beensuggested. The walls of the container, for example, can be provideddifferent configurations and angles, and different types of dischargemeans can be placed in the container. All these solutions, however, havedisadvantages, and therefore the problem at least partially remains.

SUMMARY OF THE INVENTION

[0004] In accordance with the present invention, these and otherproblems have now been realized by the invention of a container forcollecting and discharging particulate lignocellulosic materialcomprising a substantially cylindrical upper portion having a firstcross-section, a lower portion tapering from the substantiallycylindrical upper portion to a bottom defining an elongated space, anexit pipe disposed below the bottom of the container, the exit pipehaving a second cross-section and disposed substantially centrally belowthe elongated space, the second cross-section being less than the firstcross-section, a pair of parallel screws mounted on a pair of parallelshafts disposed in the elongated space in a common horizontal plane, thepair of parallel screws being adapted to feed the particulatelignocellulosic material towards the exit pipe, a pair of distributorsfor the particulate lignocellulosic material disposed on the respectivepair of parallel screws at a location above the exit pipe, the pair ofdistributors comprising a pair of substantially radial discs, and a pumpdisposed below the exit pipe for transporting the particulatelignocellulosic material to a subsequent step. Preferably, the screwscomprise threads including flanks having an upper portion adapted forconveying the particulate lignocellulosic material, the bottom definingthe elongated space having a configuration including a raised portiondefining an upper edge, the upper portion of the thread flanks beingdisposed above the upper edge of the elongated space. In a preferredembodiment, the pair of parallel shafts includes a central axis disposedsubstantially at the upper edge of the elongated space.

[0005] In accordance with one embodiment of the container of the presentinvention, the threads include intermediate spaces between the threadswhich increase in the direction towards the exit pipe. Preferably, thethreads have an increasing pitch in the direction towards the exit pipe.In another embodiment, however, the pair of parallel shafts includes adiameter which decreases in the direction towards the exit pipe.

[0006] In accordance with one embodiment of the container of the presentinvention, the substantially radial discs have a disc diameter and thescrew threads have a thread diameter, the disc diameter beingsubstantially the same as the thread diameter. In a preferredembodiment, the substantially radial discs have a center and a thicknesswhich decreases outwardly from the center.

[0007] In accordance with one embodiment of the container of the presentinvention, the container includes entry means for addition of atreatment medium into the elongated space.

[0008] The present invention offers a solution to the above-notedproblems in that the bottom of the container is provided with adischarge device comprising two counter-rotating parallel screws locatedabove a narrow down pipe.

[0009] According to the present invention, a substantially cylindricalcontainer converges at its lower portion from two opposed sides down toan oblong space in the bottom of the container. In that oblong space,which in one embodiment has a substantially rectangular cross-section,or at its ends has a rounded cross-section, two co-operatingcounter-rotating screws are placed. The screws are placed adjacent toeach other without a partition wall, and the shafts of the screws arehorizontal and in parallel, and are located in the same horizontalplane.

[0010] The central line of the shaft of each screw is preferably placedat the same level as the upper edge of the space, or the shafts areplaced so that at least the upper edge of the thread flanks of thescrews is located above the upper edge of the space. The bottom of thespace is preferably adapted to the diameter of the screw threads so thata longitudinal edge is formed between the screws. A narrow down pipe isconnected to the bottom of the space for receiving the materialdischarged from the container. The down pipe preferably has a diametercorresponding to the width of the space.

[0011] According to a preferred embodiment of the present invention, thedown pipe is placed centrally beneath the container, and the screws arearranged to feed the material from two directions inwardly towards thedown pipe. Alternatively, the down pipe can be placed at one end of theoblong space, and the screws are formed for feeding only in thatdirection.

[0012] It is suitable according to the present invention to form thescrews with a space between the threads increasing in the directiontowards the down pipe. This can be achieved by the thread pitchincreasing in the direction towards the down pipe or by the diameter ofthe shafts of the screws decreasing in the direction towards the downpipe, or by a combination of these alternatives. In this manner, moreuniform feeding of the material can be maintained across thecross-section of the container.

[0013] According to another preferred embodiment of the presentinvention with a centrally located down pipe, each screw is formed witha distributor in the form of a radial disc located centrally above thedown pipe. The disc should have a diameter corresponding to the diameterof the screw threads, and it should have a thickness decreasing towardsthe circumference thereof. By this design the feed down through the downpipe is improved to an even greater extent.

[0014] According to another embodiment of the present invention, thedown pipe is located directly above a pump, by which the material feddown through the down pipe is pumped to a subsequent treatment step. Asthe discharge screws bring about a uniform discharge from the container,the flow through the pump also becomes uniform and stable, which resultsin high operation safety and uniform treatment of the material.

[0015] According to another embodiment of the present invention, supplymeans for the addition of a treatment medium is connected to thedischarger. This supply means is preferably formed with a plurality ofnozzles for supply of the medium along the length of each screw,preferably through the walls of the space beneath the container at thesame level as the shafts of the screws. This position is especiallyfavorable for supply of the medium, because the material is in motionand, thus, the admixing will be good.

BRIEF DESCRIPTION OF THE DRAWINGS

[0016] The present invention is described in greater detail in thefollowing detailed description, which, in turn, refers to theaccompanying Figures illustrating an embodiment of the presentinvention, in which:

[0017]FIG. 1 is a side, elevational view of a container in accordancewith the present invention;

[0018]FIG. 2 is a front, elevational view of the container shown in FIG.1; and

[0019]FIG. 3 is a top, elevational view of the container shown in FIGS.1 and 2.

DETAILED DESCRIPTION

[0020] The embodiment of the present invention shown in the drawingscomprises a container 10, which has a cylindrical upper portion 11 and alower portion 12, which converges from opposed sides to a space 13 atthe bottom of the container. This space 13 has a substantiallyrectangular cross-section and is adapted to two feed screws, 14 and 15,which have horizontal and parallel shafts located in a common horizontalplane. The screws are provided with threads for feeding the material andare arranged so that the outer circumferences of the screw threads arelocated at a small distance from each other without a partition wallbetween the screws.

[0021] The thread flanks of the screws, 14 and 15, extend upwards abovethe upper edge of the space 13. The bottom of the space 13 follows thediameter of the screw threads whereby a longitudinal edge 22 is formedbetween the screws, 14 and 15. The edge 22 is located highest at thesame level as the center line of the screws.

[0022] Centrally, beneath the space 13, a down pipe 16 is connected forreceiving material from the container. The down pipe 16 has a diametercorresponding to the width of the space 13. The screws, 14 and 15, areformed with threads for feeding the material inwardly toward the downpipe 16. The rotational direction of the screws is opposed, so that theupwardly turned portion of the screws moves from the outer wall of thespace 13 inwardly toward the center of the space. This requires that thethread pitch at the end of a screw, 14 and 15, is opposed. Centrally oneach screw, 14 and 15, a distributor 17 is located. This distributor 17is formed with a radial disc, the thickness of which decreasessuccessively from the center outwardly to its circumference. Thedistributor 17 has the same diameter as the screw thread, and its objectis to interrupt the axial feed of the screws and direct the materialdown into the down pipe 13.

[0023] The screws, 14 and 15, are driven each by its motor, 18 and 19,at uniform speed, and the two screws suitably have the same speed. Inorder to additionally ensure that the material is fed from the entirecross-section of the container, the screws can be formed with a spacebetween the threads increasing inwardly to the down pipe, for exampleincreasing thread pitch or decreasing screw shaft diameter.

[0024] Beneath the down pipe 13 a pump 20 is located. The pump inlet isthus directly connected to the down pipe, which implies that the pump 20can deliver a uniform outgoing material flow to a subsequent treatmentstep.

[0025] According to the embodiment shown in the drawings, a plurality ofnozzles 21 are connected to the space 13 for the supply of treatmentmedium in the form of a gas or liquid, such as steam and chemicals.These nozzles 21 are located at both long sides of the space 13 at thesame height as the shafts of the screws so that optimum admixing to thematerial is obtained.

[0026] By forming the container with a discharger with two feed screwsaccording to the present invention it has proved possible to improve thedischarge and effectively to prevent the material from adhering or beingfed non-uniformly in the container. It is, at the same time, possible toobtain an even and operationally safe pumping of the material directlyfrom the discharge out of the container to subsequent treatment steps.

[0027] Although the invention herein has been described with referenceto particular embodiments, it is to be understood that these embodimentsare merely illustrative of the principles and applications of thepresent invention. It is therefore to be understood that numerousmodifications may be made to the illustrative embodiments and that otherarrangements may be devised without departing from the spirit and scopeof the present invention as defined by the appended claims.

1-7. (canceled).
 8. A container for collecting and dischargingparticulate lignocellulosic material comprising a substantiallycylindrical upper portion having a first cross-section, a lower portiontapering from said substantially cylindrical upper portion to a bottomdefining an elongated space, an exit pipe disposed below said bottom ofsaid container, said exit pipe having a second cross-section anddisposed substantially centrally below said elongated space, said secondcross-section being less than said first cross-section, a pair ofparallel screws mounted on a pair of parallel shafts disposed in saidelongated space in a common horizontal plane, said pair of parallelscrews being adapted to feed said particulate lignocellulosic materialtowards said exit pipe, a pair of distributors for said particulatelignocellulosic material disposed on said respective pair of parallelscrews at a location above said exit pipe, said pair of distributorscomprising a pair of substantially radial discs, and a pump disposedbelow said exit pipe for transporting said particulate lignocellulosicmaterial to a subsequent step.
 9. The container of claim 8 wherein saidscrews comprise threads including flanks having an upper portion adaptedfor conveying said particulate lignocellulosic material, said bottomdefining said elongated space having a configuration including a raisedportion defining an upper edge, said upper portion of said thread flanksbeing disposed above said upper edge of said elongated space.
 10. Thecontainer of claim 9 wherein said pair of parallel shafts includes acentral axis disposed substantially at said upper edge of said elongatedspace.
 11. The container of claim 9 wherein said threads includeintermediate spaces between said threads which increase in the directiontowards said exit pipe.
 12. The container of claim 11 wherein saidthreads have an increasing pitch in said direction towards said exitpipe.
 13. The container of claim 11 wherein said pair of parallel shaftsincludes a diameter which decreases in said direction towards said exitpipe.
 14. The container of claim 9 wherein said substantially radialdiscs have a disc diameter and said screw threads have a threaddiameter, said disc diameter being substantially the same as said threaddiameter.
 15. The container of claim 14 wherein said substantiallyradial discs have a center and a thickness which decreases outwardlyfrom said center.
 16. The container of claim 8 including entry means foraddition of a treatment medium into said elongated space.